interface Animal {
    name: string;
    age: number;
}

interface Dog extends Animal {
    eat(str: string): void
}

class WolfDog implements Dog {
    name: string;
    age: number;
    eat(str: string): void {
        console.log(str);
    }

    constructor(name: string, age: number) {
        this.name = name
        this.age = age
    }
}

var w: WolfDog = new WolfDog("狗", 8);